The present invention relates broadly to a surveillance sensor, and in particular to an optical surveillance sensor, a microprocessor-controlled RF apparatus having a compound eye configuration.
The state of the art of optical sensors is well represented and alleviated to some degree by the prior art apparatus and approaches which are contained in the following U.S. Patents:
U.S. Pat. No. 4,465,940 issued to Graff et al. on Apr. 29, 1986;
U.S. Pat. No. 4,585,937 issued to Schneider on Apr. 29, 1986;
U.S. Pat. No. 4,585,948 issued to Schneider et al. on Apr. 29, 1986;
U.S. Pat. No. 4,630,902 issued to Mochizuhi et al. on Dec. 23, 1986;
U.S. Pat. No. 4,650,279 issued to Magee on Mar. 17, 1987; and
U.S. Pat. No. 4,703,168 issued to Olson on Oct. 27, 1987.
The Graff patent is directed to an electro-optical target detection apparatus which utilizes a signal processing circuit for combining data from several spectral bands to enhance the signal-to-background ratio of a target detection system. Two spectral bands, with separate sensing arrays, receive analog signals which are fed to separate multiplexer units. From the multiplexers, the analog signals are applied to a comparator where they are compared with each other and also separately applied to shift registers where the signals are retained for further processing. If, during comparison, the ratio of the two bands is less than a threshold, there is an absence of cloud return and the signals stored in both shift registers are combined in a final output register. If the ratio of the two bands is more than a threshold, the band having the most cloud return is not used and the shift register containing the greater percentage of target return is processed through the output register.
The Schneider patent relates to a high efficiency fiber-shaped detector having a longitudinally extending core transparent to the wavelength of an incoming beam of electromagnetic radiation. Circumscribing the core and deposited thereon is an extremely thin layer of photosensitive material, an extremely thin layer of insulation and an extremely thin layer of reflective material. The photosensitive layer converts the electromagnetic radiation into an electrical signal which is transmitted to a processing system. Upon receiving the incoming beam of electromagnetic radiation, the reflective layer reflects this beam so that the beam passes through the photosensitive layer many times.
The Schneider et al. patent describes a non-scanning integrated optical system with wide field of view-search capabilities that is realized without scanning or moving parts by means of an integrated multiaperture optical system. The system utilizes light gathering optics in the form of an array of eyelets or lens apertures that direct in-coming light onto a detector layer. The detection layer consists of individual detectors, more than one to a lens. Under the detector layer there is a correlation layer, which contains a memory cell for each detector and circuitry which connects to neighboring memory cells according to a hard wired program. Below the correlation layer is a processing layer which contains microprocessor circuitry allowing further processing of the acquired information.
The Mochizuki et al. patent discloses a compound eye optical system having a variable magnification function including a first imaging element array having a plurality of imaging elements of the same focal length at an equal pitch, a second imaging element array having a plurality of imaging elements of the same focal length arranged at a pitch different from that of the first imaging element array, the second imaging element array disposed more adjacent to the image side than the first imaging element array, and means for varying the imaging magnification of a composite optical system comprising the first and second imaging element arrays.
The Magee patent teaches a fiber optic lens which includes an input aperture and a fiber optic array interconnecting the input and output apertures, including multiplicity of single mode fiber optic elements of equal optical path length for transmitting light rays in-phase from the input aperture to the output aperture; the fiber optic elements are interconnected at the same relative location at each aperture for receiving the wave front at the input aperture and producing an image at the focal point of the output aperture and having a diffraction limit which is a function of the diameter of the entire fiber optic array.
The Olson patent relates to a two-dimensional energy position detector which includes an array of wedge-shaped anodes arranged in an alternating sequence. Each of the anodes is connected to a multiplexer which is controlled by a sequencer to place the signals from the anodes in a predetermined sequence onto a multiplex output line. A data processor may then analyze the signal on the multiplex output line to determine the position of energy incident on the anodes.
In the prior art, it is clear that a need exists to provide a lightweight and comprehensive sensor system which can provide a coverage of 2 pi steradians, and can be made very inexpensively. A sensor system which does not involve any large moving parts or optic devices, can satisfy that need. In addition, there exists a need for a sensor system that can detect targets which are 90 degrees off the central optical axis and which through signal processing (sequential signal processing) can vector the sensor system such that the central optical axis is coincident with the primary target image. A sensor system with the potential for combining both radar and optical sensors by means of signal processing, can benefit from the detected and different energy spectrums from a given target. The inherent EMI immunity of a sensor system utilizing optical fibers, will provide the means to channel detected photons (UV-visible-IR) around a radar antenna to the required detector units.
The present optical surveillance apparatus may be utilized in a stationary surveillance mode wherein a sensor configuration which provides 2 pi steradians coverage (or more) could have an image template (in memory) of its static background FOV and then compare image at predetermined time intervals for any changes. The rate at which the sensor looks or compares its instantaneous FOV with that in the template memory will depend upon the particular application and the field of view conditions.
For high speed applications, a sensor mounted on a high speed platform could be designed to detect targets 90 degrees or more off its velocity vector and through internal software handoffs align the velocity vector to the primary detected object image. This high speed application could also be used to control the direction of a movable platform (fixed ground position) to track the motion of a detected target.
A survivable sensor system may be established by a sensor which uses high temperature materials and combining the inherent EMI immunity of optical fibers, the elimination of large single piece optics and moving parts, results in a sensor system that is robust and survivable for both earth and space based systems where incident light may have higher power deposition (watts/cm2).